CH647523A5 - SOLVATES OF ALICYCLIC ETHERS AND CEPHEM-4-CARBOXYLIC ACID, THEIR PREPARATION AND THEIR USE FOR OBTAINING THE ACID AND ITS SALTS. - Google Patents

Description

The present invention relates to new cephalosporin solvates, methods for their preparation and their use in the separation of the parent acid cephalosporin, or its salts.

US Patent No. 4152432 describes, inter alia, syn - 7- [2- (2-amino-4-thiazolyl) -2-methoxyimino] acetamido-3-acetoxy-methyl-3-cephem-4 acid -carboxylic, hereinafter called compound A, an important antibiotic. The aforementioned patent describes the solvates of compound A formed with formic acid and ethanol (fornic solvate and ethanolic solvate), solvates which can be used for the purpose of crystallization.

Although many cephalosporin solvates have been described previously in the literature, it is known that no one can predict that a cephalosporin will form solvates, much less which solvents will be suitable in any given case. In this regard, it will be noted that various salts, esters and derivatives with a protected amino group of compound A have been treated with alicyclic ethers in the literature (see for example the patents of EUA Nos. 4152432 and 4098888 as well as the patent description South African N ° 77/2030), but no researcher has observed the solvates which have now been discovered to form with the unprotected acid form of compound A.

It has surprisingly been found that it is possible to form solid solvates between compound A and the alicyclic ethers, provided that the solvation is carried out in an aqueous medium at a pH of 2.0 to 3.5.

According to one aspect of the invention, there is provided a solid syn-7- [2- (2-amino-4-thiazolyl) -2-methoxyimino] acetamido-3-acetoxymethyl-3-cephem-4- acid solvate. carboxylic acid and an alicyclic ether.

The alicyclic ether preferably contains from 3 to 8 carbon atoms, and better still from 4 to 6 carbon atoms. As examples of such ethers, mention may be made of tetrahydrofuran, 1,4-dioxane,

1.3-dioxolane and tetrahydropyran, which all form particularly advantageous solvates according to the invention.

The invention further provides a method of separating compound A from an aqueous reaction mixture in which the concentration of compound A is 0.07 to 0.4 mol / l, which method consists in carrying out, in the one or the other order, the stages consisting:

1) adding to the aqueous reaction mixture a certain amount of a cyclic ethereal solvent chosen from tetrahydrofuran,

1.4-dioxane, 1,3-dioxolane or tetrahydropyran, amount ranging from 0.1 volume to 2 volumes of the aqueous reaction mixture, and

2) to adjust the pH of the mixture to a value of 2.2 to 3.2, then to allow the mixture to stand until a precipitate of the solvate of compound A is formed, and to separate the precipitate.

It is difficult to separate compound A in free acid form from an aqueous reaction mixture. This difficulty is important because a clearly preferred process for synthesizing the compound is carried out in an aqueous medium (see the following examples). The ease with which the solvates of this invention precipitate from aqueous reaction mixtures therefore facilitates the separation procedure in an aqueous medium.

The aqueous reaction mixtures referred to herein are mixtures in which compound A has been synthesized. In general, the final synthesis step is the acylation step in which the [2- (2-amino-4-thiazolyl) -2-methoxyimino] -acetamido side chain is attached to the cephalosporin nucleus. Acylations of this type are preferably carried out in reaction media in which the solvent is water or an organic solvent miscible with aqueous water, in particular aqueous acetone.

When the reaction solvent in the final synthesis step is an aqueous organic solvent, it is necessary to evaporate a large amount of organic solvent before separating the compound A. Thus, the mixture in which the solvents form is called here an aqueous reaction mixture. It is obviously not necessary to remove all traces of organic solvent before adding the cyclic ether which will form the solvate. The exact amount of organic solvent which can be left in the aqueous reaction mixture depends on the temperature, the concentration of compound A in the aqueous reaction mixture and the amount of alicyclic ether which it is desired to use. In general, however, the amount of organic solvent should be reduced to less than about 1 to 10% by volume before adding the solvent forming the solvate.

The concentration of compound A in the aqueous reaction mixture is preferably from 0.07 to 0.4 mol / l. However, the concentration of compound A must be adjusted to obtain an optimal yield in the synthesis process in which it is formed, and therefore it is not normally possible to adjust the concentration exclusively for the most efficient operation of the isolation process. However, it is preferred to prepare the solvates from an aqueous reaction mixture in which the concentration of compound A is 0.1 to 0.25 mol / l.

The temperature at which the solvates are formed will also be close to room temperature instead of the process. That is to say, it will generally be between 15 and 35 ° C. However, the temperature is not decisive with respect to the separation process; solvate can form and precipitates at temperatures from 0 to

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40 ° C. When using a lower temperature, it can be expected that the solvate will precipitate more quickly and completely, but associated impurities may also precipitate in larger quantities. Thus, the operating temperature is chosen for the best convenience in the process concerned.

The precipitation of the solvate of compound A can be carried out by adding the alicyclic ethereal solvent to the aqueous reaction mixture, and adjusting its pH to a value of 2.0 to 3.5. These two steps can be done in any order, but it is best to add the solvent first.

The amount of solvent to be added can vary over wide limits. Amounts ranging from 0.1 to 2 volumes of the reaction mixture can be used; amounts ranging from about 0.25 to 0.7 times this volume are preferred. The amount of solvent to be used depends in part on the concentration of compound A in the aqueous reaction mixture, since obviously enough solvent must be used to form the solvate. It would be less economical, although possible, to use less solvent than necessary to form a solvate with all of the compound A present. Depending on the nature of the impurities present in the aqueous reaction mixture, an excess of solvent, above the amount necessary to form the solvate, can make it possible to maintain the impurities in solution while the solvate precipitates.

The pH of the mixture is adjusted to a value of 2.0 to 3.5, preferably 2.2 to 3.2, more preferably 2.2 to 3.0 and more preferably about pH 2.7. The addition of an acid is necessary to obtain a pH in the desired range. The choice of acid is not critical, but it is more convenient to use a strong and inexpensive mineral acid such as hydrochloric acid or sulfuric acid. There is, however, no objection to using any reasonably strong acid which will not react with compound A or the solvent forming the solvate. For example, phosphoric acid, methanesulfonic acid, toluenesulfonic acid or trifluoroacetic acid can be used if they are convenient in any given case.

The mixture containing the solvent is then left to stand, with or without stirring, until a precipitate of the solvate of compound A is formed. More suitably, the mixture is simply left to stand without stirring at room temperature, as described above. There is no objection to cooling the mixture to a temperature of about 0 ° C, for example, and it is also possible to isolate the solvate if the mixture is reheated, even to about 40 ° C. However , precipitation of impurities at low temperatures can counterbalance the rate of precipitation of the solvate at such temperatures. Obviously, the use of high temperatures is less economical due to the increased solubility of the solvate at such temperatures. It is therefore generally uneconomical to carry out the process at temperatures other than the ambient temperature range.

When the precipitation of the solvate of compound A has been carried out to the desired degree, the solvate is separated by filtration, centrifugation or any other suitable means. The mixture is allowed to stand for a relatively short period of time ranging from a few minutes to about 24 hours, depending on the concentration of compound A in the initial aqueous reaction mixture, the temperature and the nature of the associated impurities. The optimal period for precipitation is easily determined in any given case and depends on the relative importance which the operator attaches to obtaining complete precipitation compared to a short reaction time; a typical period is around 30 min to 2 h.

The solvent can be used in solvate form as an intermediate for processing, for example for the preparation of salts of compound A which it is desired to use as antibiotics. The salts, in particular the sodium salt, constitute the usual pharmaceutical form. The solvate can also be dried exhaustively, for example under vacuum at moderately high temperatures of between about 40 and about 60 ° C., to obtain compound A in free acid form, generally containing a certain amount of residual solvent for forming the solvate.

The following examples illustrate the separation method of this invention. The solvates are identified by nuclear magnetic resonance (NMR) analysis at 60 MHz in DMSOd6.

The products of the examples below are dried under vacuum at 40 ° C for 16 h before analysis.

The first group of examples illustrates variants of the preferred methods for carrying out the separation according to the invention.

Example 1:

45.5 g of 7-aminocephalo-sporanic acid p-toluenesulfonate are added to 400 ml of acetone and 400 ml of water, and 85 ml of a 45% solution of tripotassium phosphate is added to adjust the pH. at 7.5. The mixture is stirred for 30 min and 39.7 g of a mixture of 1H-benzotriazol-l-yl syn- (2-amino-4-thiazolyl) (methoxyimino) acetate and the internal hydroxide of syn- 1 - [(2-amino-4-thiazolyl) (methoxyimino) acetyl] -3-hydroxy-1H-benzotriazolium. Then the reaction mixture is stirred for 4 h, while maintaining the pH at 7.5 by optional addition of a tri-potassium phosphate solution.

Then the acetone is removed from the mixture by vacuum evaporation and the pH is adjusted to 4.0 with approximately 50 ml of 6N hydrochloric acid. 200 ml of tetrahydrofuran are added, the mixture is stirred for 5 min and then the pH is adjusted to 2.8 with additional hydrochloric acid. Then the acid mixture is stirred at room temperature for 90 min and filtered. The solids are washed with water and dried, giving 26.0 g of the tetrahydrofuran solvate of compound A, containing 0.6 moles of tetrahydrofuran per mole of compound A.

Compound A is identified by NMR, with the following characteristics:

S 9.83 (d, 8 Hz, H), 7.32 (s wide, 2H), 6.81 (s, H), 5.87 (dd, 8 Hz + 5 Hz, H), 5.20 (d, 5 Hz, H), 4.92 (q, 14 Hz + 9 Hz, 2H), 3.90 (s, 3H), 3.60 (s, 2H), 2.07 (s, 3H) .

The presence and the quantity of tetrahydrofuran are indicated by its characteristics in the NMR spectrum at S1.7-9.9 (m).

Example 2:

Compound A is prepared as described in Example 1, but the starting material consists of 77.8 g of 7-aminocepha-losporanic acid wet with acetone, containing 35% of pure compound. The solvate is formed and isolated as described in Example 1, but the reaction mixture is allowed to stir at room temperature for 1 h and 40 min after bringing the pH to 2.7 in the final stage of process. The solids are dried and 26.8 g of solvate are obtained, containing 0.5 g of tetrahydrofuran per mole of compound A, as shown by the NMR analysis.

Then the above solvate is recrystallized by dissolving it in 600 ml of water and 200 ml of tetrahydrofuran, by adding approximately 45 ml of a 45% aqueous solution of tripotassium phosphate. The solution is filtered through a filter aid pad and then the pH is brought to 2.7 by the addition of hydrochloric acid. An additional 100 ml of tetrahydrofuran is added and the mixture is stirred at room temperature for 15 min then in an ice water bath for 15 min, and left in the refrigerator overnight. The mixture is filtered and the solids are dried to give 20.0 g of the tetrahydrofuran solvate of compound A.

Example 3:

Compound A is prepared as described in Example 2 and its tetrahydrofuran solvate is prepared and separated as described in Example 2, but, after having adjusted the pH to 2.6 in the final step, the mixture is stirred. mix at room temperature for 30 min then in an ice water bath for 70 min. Then the mixture is filtered cold and the solids are dried to obtain 29.6 g of the tetrahydrofuran solvate of compound A, containing 0.5 mol of tetrahydrofuran per mole of compound A.

The preceding product is recrystallized by dissolving it in a mixture of water and tetrahydrofuran as described in step re5

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crystallization of Example 2. The resulting solution is stirred for 30 min, its pH is adjusted to 2.8 with normal hydrochloric acid and then stirred for 30 min at room temperature and for 60 min in a bath of ice water. The mixture is filtered and the solids are dried to obtain 24.7 g of the tetrahydrofuran solvate of compound A, containing 0.5 mol of tetrahydrofuran per mole of compound A.

The following examples describe additional methods for effecting separation according to this invention.

Example 4:

Compound A is synthesized as described in Example 2, but the reaction mixture is stirred at room temperature for 2 h and then kept overnight in the refrigerator, after addition of the mixed acylating agents. Then the acetone is removed by evaporation under vacuum and the pH of the aqueous reaction mixture is adjusted to 4.0 by addition of 6N hydrochloric acid. The mixture is then extracted three times with 220 ml portions of ethyl acetate. Then the pH of the aqueous phase left after extraction is adjusted to 2.6 with additional hydrochloric acid and 100 ml of tetrahydrofuran are added. 300 ml of water and 100 ml of additional tetrahydrofuran are added, and the mixture is stirred while the precipitate of solvate is formed. Then the mixture is filtered and the solids are washed with acetone, and 21.5 g of tetrahydrofuran solvate of compound A are obtained, containing 0.3 mol of tetrahydrofuran per mole of compound A.

The following example shows that the presence of other organic solvents does not hinder the separation step.

Example 5:

Compound A is synthesized as described in Example 4. Then the acetone is evaporated and the pH is adjusted to 4.0 as described in Example 4. 250 ml of a 1: 1 acetate mixture are added ethyl and tetrahydrofuran and stirred for a few minutes. The organic phase is separated and a heavy white precipitate separates from the aqueous phase. The extraction is repeated four times, but no additional precipitation occurs. The precipitate is separated by filtration and dried, which gives 18.2 g of the tetrahydrofuran solvate of compound A, containing 0.4 mol of tetrahydrofuran per mole of compound A.

The following example illustrates the use of a solvate according to this invention as a starting material for the preparation of salts of compound A.

Example 6:

14.5 g of the tetrahydrofuran solvate of compound A, prepared in Example 5, are suspended in 80 ml of water and the mixture is cooled in an ice bath. The pH is adjusted to 6.0 by adding a 2N solution of sodium hydroxide and the mixture is discolored by adding charcoal and filtering through a talc pad. Then the mixture is lyophilized and 12.6 g of the sodium salt of compound A containing 6.62% of water are obtained.

Example 7:

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Stir 37.8 g of 7-aminocephalosporanic acid wetted with acetone and 36% pure in 200 ml of water and 200 ml of acetone and the pH is adjusted to 7.5 by adding an aqueous solution to 45% tripotassium phosphate. Then 19.6 g of the internal hydroxide salt of syn-1 - [(2-amino-4-thiazolyl) (methoxyimino) -acetyl] -3-hydroxy-1H-benzotriazolium are added all at once and the mixture is stirred with room temperature for 4 h while maintaining the pH between 7.3 and 7.5. Then the acetone is removed by evaporation under vacuum and the pH is adjusted to 4.0 by addition of approximately 20 ml of 6N hydrochloric acid. The mixture is filtered.

To 118 ml of filtrate, 40 ml of tetrahydrofuran are added and the pH is adjusted to 2.6 with additional hydrochloric acid. The mixture is stirred for 5 min at room temperature and then kept for 16 h in a refrigerator. The mixture is stirred for 5 min in an ice water bath and filtered. The solids are washed with a small amount of water and dried. 6.44 g of the tetrahydrofuran solvate of compound A are obtained, containing approximately 1 mol of 1-hydroxybenzotriazole and approximately 0.4 mol of tetrahydrofuran per mole of compound A.

To an equal portion of the above aqueous reaction mixture, 40 ml of 1,4-dioxane is added and the mixture is treated as described in the preceding paragraph. The solids are found to constitute 6.22 g of the solvate of compound A, as shown by the NMR analysis, containing approximately 0.7 mol of 1,4-dioxane per mole of compound A. The presence and the quantity of solvent are indicated by its characteristic in the NMR spectrum at S 3.55 (s). The solvate also contains about 2 mol of 1-hydroxybenzotriazole per mole of compound A.

Example 8:

Compound A is synthesized as described in Example 7. The volume of the aqueous reaction mixture after adjusting the pH to 4.0 is 355 ml. To half of the aqueous reaction mixture, 59 ml of 1,3-dioxolane is added, the pH is adjusted to 2.6 and the resulting mixture is kept overnight in a refrigerator. The mixture is then filtered and the solids are rinsed with water, then they are dried under vacuum at 40 ° C. and 10.5 g of the solvate of compound A are obtained, containing 0.8 mol of 1.3- dioxolane per mole of compound A, value determined by NMR analysis which has the characteristics of 1,3-dioxolane at 8 3.75 (s) and 4.77 (s).

Example 9:

Compound A is synthesized as described in Example 8 above. The volume of the aqueous reaction mixture is 360 ml after adjusting the pH to 4.0, which volume is separated into two equal parts.

To one portion, 60 ml of tetrahydrofuran are added and the pH of the mixture is adjusted to 2.6 by addition of approximately 10 ml of 6N hydrochloric acid. The suspension is stirred for 30 min at room temperature and then filtered. The solids are rinsed with water and dried, and 3.41 g of the tetrahydrofuran solvate of compound A containing 0.3 mol of tetrahydrofuran per mole of compound A are obtained, by NMR analysis. Analysis by gas chromatography indicates the presence of 5.1% of tetrahydrofuran, corresponding to 0.34 mol of tetrahydrofuran per mole of compound A.

To the other portion of the aqueous reaction mixture, 60 ml of 1,4-dioxane is added and then the mixture is treated as described in the preceding paragraph to obtain 1.94 g of the solvate of compound A, containing 0.3 mol 1,4-dioxane per mole of compound A, according to NMR analysis. Analysis by vapor chromatography indicates 3.5% of 1,4-dioxane, equivalent to 0.18 mol of 1,4-dioxane per mole of compound A.

Example 10:

The process of Example 9 is repeated, but the solvents used for the formation of solvates are changed.

To half of 350 ml of an aqueous reaction mixture, 57 ml of 1,3-dioxolane are added and the pH is adjusted to 2.6 with 6N hydrochloric acid. The mixture is stirred for 30 min and filtered. The solids are washed with water and dried under vacuum for 16 h at 45 ° C. and 3.22 g of the 1,3-dioxolanic solvate of compound A are obtained. The NMR analysis indicates that the solvate contains 0.4 mol of 1,3-dioxolane per mole of compound A. Analysis by vapor phase chromatography of the solvate indicates 4.8% of 1,3-dioxolane, equivalent to 0.30 mol of 1, 3-dioxolane per mole of compound A.

To the other half of the aqueous reaction mixture, 25 ml of tetrahydropyran is added and the pH is adjusted to 2.6 as usual.

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The mixture is then stirred for 30 min at room temperature and filtered. The solids are rinsed with water and dried under vacuum for 16 h at 45 ° C and 8.77 g of the tetrahydro-pyrannic solvate of compound A are obtained, the NMR analysis of which shows that it contains a little 1-hydroxybenzotriazole. NMR analysis of the solvate indicates 0.6 mol of tetrahydropyran per mole of compound A. The NMR characteristic of tetrahydropyran is seen at 1.5-1.7 (m). Analysis by vapor chromatography indicates 5.9% tetrahydropyran, equivalent to 0.32 mol of tetrahydropyran per mole of compound A.

Claims (11)

647,523 1. Solid syn-7- [2- (2-amino-4-thiazolyl) -2-meth-oxyimino] acetamido-3-acetoxymethyl-3-cephem-4-carboxylic acid and an alicyclic ether. 2. Solid solvate according to claim 1, characterized in that the alicyclic ether is tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane or tetrahydropyran. 2 3. Process for the preparation of a solid solvate according to one of claims 1 or 2, characterized in that the said cephem acid is combined in an aqueous medium with the said alicyclic ether at a pH of 2.0 to 3, 5. 4. Method according to claim 3 for isolating syn-7- [2- (2-amino-4-thiazolyl) -2-methoxyimino] acetamido-3-acetethoxymethyl-3-cephem-4-carboxylic acid in the form of '' an alicyclic ether solvate from an aqueous mixture containing this acid in an amount of 0.07 to 0.4 mol / l, characterized in that, in any order, A) an alicyclic ether chosen from tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane and tetrahydropyran is added to the aqueous mixture, in an amount of 0.1 to 2 volumes of the aqueous mixture, and B) the pH of the mixture is adjusted to a value of 2.2 to 3.2, then the mixture is left until a precipitate of the above solvate of cephem acid is formed, and this precipitate is collected. 5. Method according to claim 4, characterized in that the concentration of cephem acid in the aqueous mixture is 0.1 to 0.25 mol / 1. 6. Method according to one of claims 4 or 5, characterized in that the alicyclic ether is added before adjusting the pH. 7. Method according to one of claims 3 to 6, characterized in that the pH is adjusted to a value between 2.2 and 3.0. 8. Method according to one of claims 3 to 7, characterized in that it is carried out at a temperature of 15 to 35 ° C. 9. Process for obtaining free syn-7- [2- (2-amino-4-thiazolyl) -2-methoxyimino] acetamido-3-acetoxymethyl-3-cephem-4-carboxylic acid, characterized in that it consists in removing the alicyclic ether from the solvate obtained by the process according to claim 4. 10. The method of claim 9, to obtain a salt of the cephem acid indicated, characterized in that the alicyclic ether is removed from the solvate by neutralization of the latter by means of a suitable base added. 11. Syn-7- [2- (2-amino-4-thiazolyl) -2-methoxyimino] acet-amido-3-acetoxymethyl-3-cephem-4-carboxylic acid or a salt thereof, obtained by the process according to claims 9 and 10.